Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Furthermore, as an air conditioner which is applicable to such a vehicle, there has been developed an air conditioner which includes a compressor to compress and discharge a refrigerant, a radiator (a condenser) disposed in an air flow passage of a vehicle interior to let the refrigerant radiate heat, a heat absorber (an evaporator) disposed in the air flow passage to let the refrigerant absorb heat, and a refrigerant circuit constituted of an outdoor heat exchanger or the like disposed outside the vehicle interior to let the refrigerant radiate or absorb heat, and which executes respective modes such as a heating mode in which the refrigerant discharged from the compressor radiates heat in the radiator and the refrigerant by which heat has been radiated in this radiator absorbs heat in the outdoor heat exchanger, a dehumidifying and heating mode in which the refrigerant discharged from the compressor radiates heat in the radiator and the refrigerant by which heat has been radiated in this radiator absorbs heat in the heat absorber and the outdoor heat exchanger or only in the heat absorber, a cooling mode in which the refrigerant discharged from the compressor radiates heat in the outdoor heat exchanger and absorbs heat in the heat absorber, and a dehumidifying and cooling mode in which the refrigerant discharged from the compressor radiates heat in the radiator and the outdoor heat exchanger and absorbs heat in the heat absorber (e.g., see Patent Document 1).
Additionally, there has been developed an air conditioner including an injection circuit which distributes a refrigerant flowing out from a radiator, decompresses this distributed refrigerant, performs heat exchange between this refrigerant and the refrigerant flowing out from the radiator, and returns the refrigerant to the middle of compression by a compressor in a heating mode, whereby the refrigerant to be discharged from the compressor is increased, and a heating capability by the radiator improves (e.g., see Patent Document 2).